Refer to the following statements:
$I$. Carbonic anhydrase is present in the erythrocytes.
$II$. In erythrocytes,the carbon dioxide combines with water and is transported.

• A
  Statement $I$ is correct and is responsible for statement $II$.
• B
  Statement $I$ is not correct but statement $II$ is correct.
• C
  Both statements $I$ and $II$ are wrong.
• D
  Statement $I$ is correct but not involved in statement $II$.